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perl-Digest-SHA - Digest-SHA - Perl extension for SHA-1/224/256/384/512
- Description:
Digest::SHA is written in C for speed. If your platform lacks a
C compiler, you can install the functionally equivalent (but much
slower) Digest::SHA::PurePerl module.
The programming interface is easy to use: it's the same one found
in CPAN's Digest module. So, if your applications currently
use Digest::MD5 and you'd prefer the stronger security of SHA,
it's a simple matter to convert them.
The interface provides two ways to calculate digests: all-at-once,
or in stages. To illustrate, the following short program computes
the SHA-256 digest of "hello world" using each approach:
use Digest::SHA qw(sha256_hex);
$data = "hello world";
@frags = split(//, $data);
$digest1 = sha256_hex($data);
$state = Digest::SHA->new(256);
for (@frags) { $state->add($_) }
$digest2 = $state->hexdigest;
print $digest1 eq $digest2 ?
"whew!\n" : "oops!\n";
To calculate the digest of an n-bit message where *n* is not a
multiple of 8, use the *add_bits()* method. For example, consider
the 446-bit message consisting of the bit-string "110" repeated
148 times, followed by "11". Here's how to display its SHA-1
digest:
use Digest::SHA;
$bits = "110" x 148 . "11";
$sha = Digest::SHA->new(1)->add_bits($bits);
print $sha->hexdigest, "\n";
Note that for larger bit-strings, it's more efficient to use the
two-argument version *add_bits($data, $nbits)*, where *$data* is
in the customary packed binary format used for Perl strings.
The module also lets you save intermediate SHA states to disk, or
display them on standard output. The *dump()* method generates
portable, human-readable text describing the current state of
computation. You can subsequently retrieve the file with *load()*
to resume where the calculation left off.
To see what a state description looks like, just run the following:
use Digest::SHA;
Digest::SHA->new->add("Shaw" x 1962)->dump;
As an added convenience, the Digest::SHA module offers routines to
calculate keyed hashes using the HMAC-SHA-1/224/256/384/512
algorithms. These services exist in functional form only, and
mimic the style and behavior of the *sha()*, *sha_hex()*, and
*sha_base64()* functions.
use Digest::SHA qw(hmac_sha256_hex);
print hmac_sha256_hex("Hi There", chr(0x0b) x 32), "\n";
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